The present invention relates generally to a process for making thermoplastic, elastomeric articles such as, for example, thermoplastic semi-pneumatic tires and, more particularly, to a process wherein a thermoplastic, elastomeric molding composition including a vulcanizable or otherwise thermosetable elastomer of the ethylene/propylene type, filler materials, a plasticizer and processing aids is admixed and then molded into thermoplastic, elastomeric articles without being vulcanized.
Thermoplastic, elastomeric articles have, in recent years, become increasingly popular due, in part, to the fact that such thermoplastic, elastomeric articles, while possessing physical properties at least as good as comparable vulcanized elastomeric articles, are more readily mass produced and, in many instances, are lower in cost than comparable thermoset articles. The elimination of the vulcanization step reduces the production time required to fabricate the articles and thus achieves a significant advantage.
Another advantage thermoplastic articles have over comparable vulcanized or thermoset articles is the ability to process scrap material or imperfect articles without the necessity of first having to devulcanize them as is generally required when reprocessing thermoset articles.
Thermoplastic, elastomeric articles have, in the past, proven commercially unacceptable in many instances, due either to their inferior physical properties or to their prohibitively high cost when compared to comparable thermoset articles. Elastomeric articles such as, for example, semi-pneumatic tires, require a fairly high tensile strength and tear strength and must be of sufficient hardness to resist wear. Additionally, such articles should have relatively high elongation since they must be capable of being stretched over a wheel center during make-up.
Against the foregoing background, it is a primary objective of the present invention to provide a process for molding a thermoplastic molding composition into a useful elastomeric article.
It is an additional object of the present invention to provide for a process for molding a thermoplastic, elastomeric molding composition into a useful elastomeric article such as, for example, a semi-pneumatic tire, having a relatively high tensile strength and high elongation.
It is another object of the present invention to provide a process for molding a thermoplastic, elastomeric molding composition into a useful thermoplastic, elastomeric article such as, for example, a semi-pneumatic tire, which possesses physical properties equal or superior to comparable thermoset elastomeric articles.